The invention belongs to the field of radar signal processing in particular for airborne weather radars.
An airborne radar comprises a transmitter which sends signals, more precisely radio waves. The latter are reflected by the target and detected by a receiver, also incorporated within the radar. The position of the targets that are in the field of the transmitted radio waves is estimated by virtue of the time they take to return. In the context of a weather application, a target may be a cloud, for example. In other words, by interpreting the waves returned by the targets, their position is deduced therefrom.
The echoes returned by the ground called “ground echoes” may be particularly obstructive for the interpretation of the received signals.
Specifically, the latter may be interpreted as signals backscattered by clouds. All the more so because, depending on the type of terrain observed, the power reflected by the ground is usually as great or even greater than that reflected by the weather phenomena, which results in the appearance of a high reflectivity value on the radar image.
The appearance of this high reflectivity value on a radar image will reflect a dangerous phenomenon and be indicated as such to the pilot, thereby creating a false alarm.
It is therefore particularly important to dispense with the ground echoes so as not to perturb the pilot.
From the prior art (U.S. Pat. No. 6,603,425, Collins) a method is known for detecting ground echoes with the aid of two horizontal sweeps, on two distinct elevation values. The latter are subtracted from one another and the resultant difference is compared with a reference value in order to determine the power due to the ground echoes.
However, this method is not very precise (because of a small number of elevation values in question), and not very robust when certain weather phenomena arise. Moreover, many accuracy problems may occur because of the time necessary to make each horizontal sweep.